FORCE OF INTRUSION
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• INTRUSION? Burstone (1977) - the apical movement of the geometric center of the root (centroid) in respect to the occlusal plane based on the long axis of the tooth.
• DEEP OVERBITE? The excessive vertical overlap of the upper anterior teeth over the lower. www.indiandentalacademy.com
• WHY DO WE INTRUDE? - Cl-II and few Cl-I malocclusions manifest deepbite - Causing an extrusion of upper anterior teeth - Leading to a gummy smile
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GUMMY SMILE
IDEAL SMILE LINE
CORRECT INCISOR RELATION
INCREASED OVERBITE
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PRINCIPLES FOR OBTAINING INTRUSION - Light and constant force - Single point of force application - Sequential intrusion - Good control of anchorage - Analysis of the forces and movements involved in the different biomechanical situations
Burstone www.indiandentalacademy.com
IDEAL FORCE REQUIREMENTS FOR INTRUSION
- 50gms total against the central incisor - 100gms(0.9n)against the incisal segment in the maxillary arch.
Burstone www.indiandentalacademy.com
• This study compares the forces exerted by the various intrusive sectional arch’s on the upper anterior teeth using different wires.
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AIMS OF THE STUDY Comparison of stresses exerted by-Utility Arch - 0.016 x 0.022 Elgiloy. -Utility Arch – 0.016 x 0.022 Stainless Steel. -Burstone Intrusion Arch (with coil) - 0.016 x 0.022 Stainless Steel. -Burstone Intrusion Arch (with coil) - 0.016 x 0.022 TMA. -Connecticut Intrusion Arch - 0.016 x 0.022 Nickel Titanium. www.indiandentalacademy.com
On the alveolar bone of maxillary incisor segment of a human skull using ‘strain gauges’ •
To compare intrusive forces produced by the same arch wires using an instron machine.
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REVIEW LITERATURE • ROBERT RICKETS (1950) - Rickets step down base arch. • CHARLES.R.BURSTONE (1977) - Intrusive arch for placement in the central incisors or four incisors. • MARC.M.VANDERBULCKE et al (1986) - Center of resistance • JAMES.A.McNAMARA (1986) - The utility arch www.indiandentalacademy.com
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BHAVANA SHROFF et al (1995) - Appliance for simultaneous intrusion and retraction of upper anterior teeth.
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VARUN KALRA (1998) - K-SIR Arch.
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RAVINDRA NANDA et al (1998) - Connecticut intrusion Arch.
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MATERIALS AND METHODS • Human skull with all well aligned maxillary teeth and good bone support. • Fitted with a 0.018 slot preadjusted edgewise bracket of roth prescription.
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ARMAMENTARIUM www.indiandentalacademy.com
WIRES AND ARCH WIRE FORMS INTRUSIVE ARCHES Burstone intrusion arch Burstone intrusion arch Utility arch
ARCH WIRE MATERIAL Stainless steel
COMPANY Straight length-unitek
TMA
Straight length-ormco
Elgiloy
Utility arch
Stainless steel
Straight length-american orthodontics Straight length-unitek
Connecticut intrusion arch
Nickel titanium www.indiandentalacademy.com
Preformed-ortho organizers
WIRE AND ARCH WIRE FORMS
Burstone Intrusion Arch 0.016”X0.022” TMA
Utility Arch 0.016” X 0.022” SS
Utility Arch 0.016” X 0.022” Elgiloy
Burstone Intrusion Arch 0.016” X 0.022” SS
Connecticut Intrusion Arch 0.016” X 0.022” Nickel Titanium www.indiandentalacademy.com
• The template was made - Pressing a softened sheet of wax onto the test jaw containing the full complement of teeth therefore creating indentations on the wax sheet. - The wax was cut and the arch form transferred to a template - All the arch forms were then made around this template. - The connecticut arch was preformed and its length adjusted and modified accordingly. www.indiandentalacademy.com
THE TESTING SYSTEM Two systems were employed 1.Strain gauge 2.Instron testing machine
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STRAIN INDICATOR
INSTRON MACHINE DIGITAL DISPLAY www.indiandentalacademy.com
STRAIN GAUGE -1mm strain gauge made of 45% nickel and 55% copper -Fixed on to the alveolar bone of each maxillary incisor at its approximate centroid -Strain gauge connected to strain indicator using an electrical wire. -Wheatstone bridge circuit to measure the strains.
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-Burstone and connecticut arches placed piggy back on the base arch wire and secured. -Strain meter ensured to check zero before each reading -Procedure repeated for each tooth. -Utility arch was tied directly onto the anterior brackets and readings recorded similarly • Five arch wires in each sample was tested and the result was calculated www.indiandentalacademy.com
• Testing method -The Youngs modulus = stress/strain -The Youngs modulus of alveolar bone = 1.4 x (10)3 kg/mm2 -Therefore 1.4 x (10)3 kg/mm2 = stress/strain - strain = value obtained from the strain indicator for individual teeth when intrusive arch was engaged. - stress was calculated subsequently substituting the values. www.indiandentalacademy.com
• Instron machine(model no.4204) - subjected intrusion arch inserted into the molar tubes accordingly -incisor brackets detached to avoid interference -levels of slots marked -skull positioned to in the desired manner -instron crosshead speed set at 2cm/min or 20mm/min www.indiandentalacademy.com
-A 1mm stainless steel hook for pulling the arch wire secured to the instron -Wire was pulled till level marked at incisors -Five different readings recorded for each intrusion arch.
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STRAIN GAUGE IN POSITION
STUDY SET-UP
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INTRUSIVE FORCES BEING MEASURED USING www.indiandentalacademy.com INSTRON
STRESS VALUES EXERTED BY DIFFERENT ARCHES ON THE ALVEOLAR BONE OF THE INCISOR SEGMENT IN GMS/MM2 GROUP
VALUES
GROUP-1 CONNECTICUT INTRUSION ARCHNICKEL TITANIUM
56.12 58.04 60.00 51.40 54.28
GROUP-2 BURSTONE INTRUSION ARCH-TMA
78.40 73.60 80.84 75.54 78.40
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87.52 GROUP-3 90.10 BURSTONE INTRUSION ARCH- STAINLESS STEEL 92.24 92.10 85.54
123.2 GROUP-4 UTILITY ACH-STAINLESS 126.6 123.2 STEEL
128.4 130.42
GROUP5 UTILITY ARCHELGILOY
150.08 153.8 156.8 153.8 150.08
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INTRUSIVE FORCES EXERTED BY DIFFERENT INTRUSIVE ARCHES EVALUATED USING A INSTRON MACHINE GROUP
VALUES
GROUP-1 CONNECTICUT INTRUSION ARSHNICKEL TITANIUM
35.12 34.96 34.95 34.96 35.00
GROUP-2 BURSTONE INTRUSION ARCH-TMA
59.20 59.45 59.50 59.35 59.50
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GROUP-3 BURSTONE INTRUSION ARCH-STAINLESS STEEL
79.91 80.01 79.35 79.61 80.23
110.00 GROUP-4 UTILITY ARCH-STAILESS 110.01 110.10 STEEL 109.90 110.10
GROUP-5 UTILITY ARCH-ELGILOY
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126.10 126.20 125.90 125.80 126.10
• The analysis used for statistically evaluating the five sets of arch wires were– THE STUDENTS ‘T’ TEST – THE ANOVA ANALYSIS
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RESULTS Arch forms that showed force in descending order: 1- UTILITY ARCH - Elgiloy (group 5) 2- UTILITY ARCH - Stainless steel(group 4) 3- BURSTONE INTRUSION ARCH - Stainless steel (group 3) 4- BURSTONE INTRUSION ARCH - TMA (group 2) 5- CONNECTICUT INTRUSION ARCH - NiTi (group 1) www.indiandentalacademy.com
STRESS VALUES EXERTED BY DIFFERENT ARCHES ON THE ALVEOLAR BONE
0 – CONNECTICUT INTRUSION ARCH 0 - BURSTONE INTRUSION ARCH – SS 0 – UTILITY ARCH – ELGILOY 0 – BURSTONE INTRUSION ARCH – TMA 0 – UTILITY ARCH - SS www.indiandentalacademy.com
INTRUSIVE FORCES EXERTED BY DIFFERENT ARCHES
0 – CONNECTICUT INTRUSION ARCH 0 - BURSTONE INTRUSION ARCH – SS 0 – UTILITY ARCH – ELGILOY 0 – BURSTONE INTRUSION ARCH – TMA 0 – UTILITY ARCH - SS www.indiandentalacademy.com
CONCLUSION • From this study it is concluded that by listing the force delivered by various intrusive arches , it is in the hands of the orthodontist to select the ideal intrusive arch depending on the needs of individual case and use his or her knowledge of bio-mechanics to get the best of results.
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www.indiandentalacademy.com Leader in continuing dental education
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